1. Field of the Invention
The present invention relates to chuck jaws, and in particular, chuck jaws used for holding irregularly shaped parts for turning on a lathe.
2. Description of the Related Art
Irregularly shaped parts often must be turned on a lathe in the course of their manufacture. Unfortunately, the irregularity of the outer surface of the object can make it difficult for the lathe chuck to hold the object without stressing it.
Take the example of the differential housing 10 shown in phantom in the drawing. The differential housing 10 has a radially large part 12 near one end and a radially small part 14 near the other end. The differential housing 10 needs to be bored at each end during the normal course of manufacture. This means that the differential housing must be held stably in the lathe, with minimal distortion to the housing due to the force of the chuck.
A conventional 3-jaw, self-centering chuck typically has been be used to grip the large (flanged) end 12 of the differential housing 10 to turn it on a lathe. While a locator may be provided to axially locate the small end 14 of the differential housing, typically there is no radial support at that end. This means that it is not unusual for the differential housing 10 to move when being bored at the small end 14. Use of a higher jaw force at the large part 12 would distort the differential housing, while providing little increase in rigidity. A further complication is that due to the normal irregularity of the casting of the housing, each of the three jaws usually will only contact only at one of the two serrations on the jaw. All of this means that only a low feed rate can be used to process differential housings through a lathe, causing long cycle times and increased costs.
One possibility for solving this problem would be to substitute a 3-jaw, pull-back chuck with solid jaws contacting on three serrations for the conventional 3-jaw, self-centering chuck. The radial and axial movement of the pull-back jaws would then provide radial and axial gripping. The disadvantage to this is that a different chuck would be required from that typically used on a conventional lathe. The chuck then would have to be changed every time part production was changed, significantly increasing change-over time and costs.